Nearly half of students in Grades 7 to 12 experience sexual harassment during the school year, according to a report out Monday – the first national study of the subject in a decade.

Adults need to create a climate that doesn’t tolerate such peer-to-peer behavior, say the report's authors – especially since only 9 percent of the targets of sexual harassment report it at school.

“Sexual harassment doesn’t get attention as much as bullying, because it’s less comfortable to talk about ... but we hope this report is one way to start a conversation” school by school, says Catherine Hill, co-author of the report and director of research at the American Association of University Women (AAUW) in Washington. “It is distinct from bullying in a number of ways ... and it has a disproportionate impact on female students.”

Fifty-six percent of girls in the nationally representative survey about the 2010-11 school year said they were sexually harassed, compared with 40 percent of boys.

Among the findings of “Crossing the Line: Sexual Harassment at School,” published by AAUW:

• 33 percent said a peer had made unwelcome sexual comments, jokes, or gestures.

• 13 percent of girls and 3 percent of boys were touched in an unwelcome sexual way.

• 4 percent of girls and 0.2 percent of boys reported being forced to do something sexual.

Students said they were eager to have anonymous ways to report such behavior, as well as structured discussions of sexual harassment and enforcement of rules against it.

AAUW is reaching out to groups such as Girls for Gender Equity, Men Can Stop Rape, and the Girls Scouts and Boy Scouts to help raise awareness about sexual harassment and prevention.

Schools need to be alert to the issue, AAUW points out, to help stop a cycle of harassment – in which those who admit to harassing their peers often have already been harassed themselves.

Many boys, for instance, report feeling upset about being called gay, and“that could prompt them to try to prove their masculinity” by going after girls in inappropriate sexual ways, says Holly Kearl, report co-author and a program manager at AAUW.

If schools neglect severe or pervasive sexual harassment, they could be held liable under Title IX, the federal law that prohibits sex discrimination in education. But as the report points out, sexual harassment can cause problems for students long before it prompts legal action.

For instance, among students who experienced sexual harassment:

• 32 percent said that afterward they did not want to go to school (and for 10 percent, this lasted quite awhile).

• 31 percent felt sick to their stomachs.

• 30 percent found it difficult to study.

• 8 percent stopped doing an activity or sport.

• 4 percent switched schools.

Educators have been able to help students stand up to sexual harassment and change the school climate, and the report highlights some examples.

Jennifer Martin, an English teacher at Tinkham Alternative High School in Westland, Mich., designed a women’s studies course in 2003 when she realized how many of the school’s girls were upset about sexual harassment by the boys, but were reluctant to report it.

“Their lives had taught them this is just how it is; this is what women have to deal with,” she says.

The course ranged from the history of women’s movements to the definition of sexual harassment and laws against it. But the first thing Ms. Martin had to do, she says, was build trust among the girls so they could help one another, instead of seeing themselves as competitors for boys’ attention.

“When they saw it was a safe place and they realized they had a common problem, then they were reporting more. And [within six weeks] they would stand up for one another in the hallways when they saw other girls being harassed,” Martin says.

While the course was recently discontinued, the culture change in the school has lasted, Martin says, partly because staff awareness grew.

The authors of “Crossing the Line” hope it will serve as a springboard for more teachers, parents, and students to initiate such prevention efforts.

“In the [popular] media, sexual harassment is often treated as a joke,” Ms. Kearl says. “So if that’s the only message students are getting, that’s problematic.”